tailcfg,hostinfo: add Hostinfo.Machine and Hostinfo.GoArchVar

For detecting a non-ideal binary running on the current CPU.

And for helping detect the best Synology package to update to.

Updates #6995

Change-Id: I722f806675b60ce95364471b11c388150c0d4aea
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

hostinfo/hostinfo.go

@@ -11,6 +11,7 @@ import (
 	"io"
 	"os"
 	"runtime"
+	"runtime/debug"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -46,7 +47,9 @@ func New() *tailcfg.Hostinfo {
 		Desktop:         desktop(),
 		Package:         packageTypeCached(),
 		GoArch:          runtime.GOARCH,
+		GoArchVar:       lazyGoArchVar.Get(),
 		GoVersion:       runtime.Version(),
+		Machine:         condCall(unameMachine),
 		DeviceModel:     deviceModel(),
 		Cloud:           string(cloudenv.Get()),
 		NoLogsNoSupport: envknob.NoLogsNoSupport(),
@@ -60,6 +63,7 @@ var (
 	distroName     func() string
 	distroVersion  func() string
 	distroCodeName func() string
+	unameMachine   func() string
 )
 
 func condCall[T any](fn func() T) T {
@@ -72,6 +76,7 @@ func condCall[T any](fn func() T) T {
 
 var (
 	lazyInContainer = &lazyAtomicValue[opt.Bool]{f: ptr.To(inContainer)}
+	lazyGoArchVar   = &lazyAtomicValue[string]{f: ptr.To(goArchVar)}
 )
 
 type lazyAtomicValue[T any] struct {
@@ -321,6 +326,27 @@ func inDockerDesktop() bool {
 	return false
 }
 
+// goArchVar returns the GOARM or GOAMD64 etc value that the binary was built
+// with.
+func goArchVar() string {
+	bi, ok := debug.ReadBuildInfo()
+	if !ok {
+		return ""
+	}
+	// Look for GOARM, GOAMD64, GO386, etc. Note that the little-endian
+	// "le"-suffixed GOARCH values don't have their own environment variable.
+	//
+	// See https://pkg.go.dev/cmd/go#hdr-Environment_variables and the
+	// "Architecture-specific environment variables" section:
+	wantKey := "GO" + strings.ToUpper(strings.TrimSuffix(runtime.GOARCH, "le"))
+	for _, s := range bi.Settings {
+		if s.Key == wantKey {
+			return s.Value
+		}
+	}
+	return ""
+}
+
 type etcAptSrcResult struct {
 	mod      time.Time
 	disabled bool

hostinfo/hostinfo_uname.go

@@ -0,0 +1,39 @@
+// Copyright (c) 2023 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux || freebsd || openbsd || darwin
+
+package hostinfo
+
+import (
+	"runtime"
+
+	"golang.org/x/sys/unix"
+	"tailscale.com/types/ptr"
+)
+
+func init() {
+	unameMachine = lazyUnameMachine.Get
+}
+
+var lazyUnameMachine = &lazyAtomicValue[string]{f: ptr.To(unameMachineUnix)}
+
+func unameMachineUnix() string {
+	switch runtime.GOOS {
+	case "android":
+		// Don't call on Android for now. We're late in the 1.36 release cycle
+		// and don't want to test syscall filters on various Android versions to
+		// see what's permitted. Notably, the hostinfo_linux.go file has build
+		// tag !android, so maybe Uname is verboten.
+		return ""
+	case "ios":
+		// For similar reasons, don't call on iOS. There aren't many iOS devices
+		// and we know their CPU properties so calling this is only risk and no
+		// reward.
+		return ""
+	}
+	var un unix.Utsname
+	unix.Uname(&un)
+	return unix.ByteSliceToString(un.Machine[:])
+}

tailcfg/tailcfg.go

@@ -528,7 +528,9 @@ type Hostinfo struct {
 	ShareeNode      bool           `json:",omitempty"` // indicates this node exists in netmap because it's owned by a shared-to user
 	NoLogsNoSupport bool           `json:",omitempty"` // indicates that the user has opted out of sending logs and support
 	WireIngress     bool           `json:",omitempty"` // indicates that the node wants the option to receive ingress connections
-	GoArch          string         `json:",omitempty"` // the host's GOARCH value (of the running binary)
+	Machine         string         `json:",omitempty"` // the current host's machine type (uname -m)
+	GoArch          string         `json:",omitempty"` // GOARCH value (of the built binary)
+	GoArchVar       string         `json:",omitempty"` // GOARM, GOAMD64, etc (of the built binary)
 	GoVersion       string         `json:",omitempty"` // Go version binary was built with
 	RoutableIPs     []netip.Prefix `json:",omitempty"` // set of IP ranges this client can route
 	RequestTags     []string       `json:",omitempty"` // set of ACL tags this node wants to claim

tailcfg/tailcfg_clone.go

@@ -137,7 +137,9 @@ var _HostinfoCloneNeedsRegeneration = Hostinfo(struct {
 	ShareeNode      bool
 	NoLogsNoSupport bool
 	WireIngress     bool
+	Machine         string
 	GoArch          string
+	GoArchVar       string
 	GoVersion       string
 	RoutableIPs     []netip.Prefix
 	RequestTags     []string

tailcfg/tailcfg_test.go

@@ -50,7 +50,9 @@ func TestHostinfoEqual(t *testing.T) {
 		"ShareeNode",
 		"NoLogsNoSupport",
 		"WireIngress",
+		"Machine",
 		"GoArch",
+		"GoArchVar",
 		"GoVersion",
 		"RoutableIPs",
 		"RequestTags",

tailcfg/tailcfg_view.go

@@ -276,7 +276,9 @@ func (v HostinfoView) ShieldsUp() bool        { return v.ж.ShieldsUp }
 func (v HostinfoView) ShareeNode() bool       { return v.ж.ShareeNode }
 func (v HostinfoView) NoLogsNoSupport() bool  { return v.ж.NoLogsNoSupport }
 func (v HostinfoView) WireIngress() bool      { return v.ж.WireIngress }
+func (v HostinfoView) Machine() string        { return v.ж.Machine }
 func (v HostinfoView) GoArch() string         { return v.ж.GoArch }
+func (v HostinfoView) GoArchVar() string      { return v.ж.GoArchVar }
 func (v HostinfoView) GoVersion() string      { return v.ж.GoVersion }
 func (v HostinfoView) RoutableIPs() views.IPPrefixSlice {
 	return views.IPPrefixSliceOf(v.ж.RoutableIPs)
@@ -310,7 +312,9 @@ var _HostinfoViewNeedsRegeneration = Hostinfo(struct {
 	ShareeNode      bool
 	NoLogsNoSupport bool
 	WireIngress     bool
+	Machine         string
 	GoArch          string
+	GoArchVar       string
 	GoVersion       string
 	RoutableIPs     []netip.Prefix
 	RequestTags     []string